The present invention relates to improvements in marine propulsion systems. More particularly, the present invention relates to a marine propulsion system incorporated into the structural design of a vessel in order to optimize energy conversion and minimize power requirements.
Motion of marine vessels is resisted by frontal impact of air and water on the vessel and by frictional drag produced by wake and turbulence as the vessel is propelled. Numerous prior art attempts have been made to overcome these problems. For example, in U.S. Pat. No. 2,348,106 to Brian et al there is disclosed a bow-mounted blower which impels frontal air through a channel to beneath the vessel where it is impacted against the wake. As a result the air not only is prevented from impeding vessel motion, but is actually used to provide a propulsive force. The Brian et al system is efficient for its purpose; however, the impacting air tends to lift the vessel and support it on a cushion of air. Such air-cushioned vessels require significant power, both to effect lift and in causing rearward water flow which is not converted to vessel motion.
An analogous approach has been attempted in a hull displacement vessel, as described in U.S. Pat. No. 2,543,024 to Humphrey. Humphrey discloses a hull-containing channel in the form of an open-ended hollow water duct extending from bow to stern along the vessel bottom. A submerged nozzle issues air into the duct to react against the water and provide a propulsive force. The Humphrey system has its virtues but has a considerable number of disadvantages. For example, the inlet end of the water duct has a relatively small opening so that the frontal impact of water on the vessel remains significant. Moreover, the submerged nozzle results in air bubbles being issued into the duct, which bubbles produce frictional losses. Further, the presence of the nozzle in the duct impedes water flow and reduces efficiency. Still further, the nozzle in Humphrey is located at the rear of the duct which turns out to be a relatively inefficient location in that the issued air has little direct effect on the water located in the duct forward of the nozzle. Still further, the Humphrey approach requires a flat-bottomed vessel which is susceptible to both roll and yaw instability.
It is therefore an object of the present invention to provide a propulsion system and interrelated structural design for a marine craft of the hull displacement type wherein motion-resisting forces and power requirements are minimized.
It is another object of the present invention to provide an improved propulsion system for a hull displacement vessel of the type having a hull-contained water duct extending throughout its length, which system eliminates impediments to water flow through the duct, applies a reactive propulsion force at the optimum location in the duct, and permits the vessel to have a configuration which imparts a high degree of stability.